Device for reducing internal combustion engine hydrocarbon emissions

ABSTRACT

A device for reducing the emission of unburned hydrocarbons from an internal combustion engine during periods of engine speed deceleration when combustion chamber and intake manifold pressures drop to such low values as to inhibit complete combustion. The low pressure or vacuum that occurs is relieved by directing an air-fuel mixture into the intake manifold whenever manifold pressure falls to a predetermined value. This mixture is formed in a secondary charge forming device that operates independently from the conventional engine carburetor.

United States Patent [72] Inventor William David Boyd Buckhurst Hill, England [2i] Appl. No. 819,329

[22] Filed Apr. 25, 1969 {45] Patented Apr. 20, 1971 [73] Assignee Ford Motor Company Deal-born, Mich.

[54] DEVICE FOR REDUCING INTERNAL COMBUSTION ENGINE HYDROCARBON EMISSIONS 5 Claims, 1 Drawing Fig.

[52] US. Cl 261/23, I23/l97, 261/69, 261/63 5 1] Int. Cl F02ni 7/12 [50] Field of Search 261/( Degassers),

[56] References Cited UNITED STATES PATENTS 2,824,726 2/1958 Dietrich et al. ..26l/( Degassers) 3,265,373 8/1966 Walker et a1. ....26l/(Degassers) 3,330,544 7/ l 967 Ozersky ..26l/(Degassers) Primary ExaminerTim R. Miles Att0rneys-John R. Faulkner and E. Dennis OConnor ABSTRACT: A device for reducing the emission of unburned hydrocarbons from an internal combustion engine during periods of engine speed deceleration when combustion chamber and intake manifold pressures drop to such low values as to inhibit complete combustion. The low pressure or vacuiii'n that occurs is relieved by directing an air-fuel mixture into the intake manifold whenever manifold pressure falls to a predetermined value. This mixture is formed in a secondary charge forming device that operates independently from the conventional engine carburetor.

Patented April 20, 1971 INVENTOR.

DEVICE FOIIR IRIEDIUCIING INTERNAL COMBUSTION ENGINE IIIIYIDIROCARBON EMISSIONS BACKGROUND OF THE INVENTION During periods of deceleration from high speed operation, extremely low pressures (high vacuums) are formed in the combustion chambers and intake manifold of an internal combustion engine. Relief of vacuums formed at such times cannot be accomplished by the entry of air through the engine carburetor because the carburetor throttle valve is closed. The vacuum formed does draw some fuel into the combustion chambers through the carburetor idle jets that are located downstream of the throttle valve. Historically, a significant portion of this fuel was exhausted unburned from the engine.

One of the factors limiting the combustion of this fuel was the lack of air available for mixing with the fuel. When this fuel reached the combustion chamber, it was part of an overly rich air-fuel mixture that would not be combusted completely under ideal conditions. An attempt to remedy this situation was the provision that the carburetor throttle valve should be held open a slight degree during high-speed engine deceleration to allow the entry of additional air to mix with the fuel to form a mixture more suitable for combustion. Such a scheme is disclosed by US. Pat. No. 2,988,074, issued .Iun. I3, I964, and is successful in reducing the emissions of unburned hydrocarbons from the engine. Complete combustion, however, is not attained by this arrangement.

It has been discovered that the low pressures present in engine combustion chambers during deceleration render it impossible for complete combustion to occur irrespective of the air-fuel mixture present in these chambers. In order for complete combustion, the vacuum developed during deceleration must be relieved. If this vacuum is relieved by admitting air through the carburetor. the resulting air-fuel mixture will be too lean to burn; while if additional fuel is admitted to relieve the vacuum, an overly rich mixture will result.

It is an object of this invention to provide a device for reducing the unburned hydrocarbon emissions of an internal combustion engine that effectively limits the pressure drop that may occur in the engine combustion chambers and intake manifold during deceleration of engine speed. This is accomplished according to this invention by relieving engine vacuum by admitting a charge to the intake manifold. This charge is an air-fuel mixture and is itself combustible. The emission control device of this invention in no way affects engine operating characteristics or efficiency during normal engine usage as this device becomes operative only during engine deceleration from high speeds. This device is of relatively simple design and offers ease and economy of manufacture.

SUMMARY OF THE INVENTION The device for reducing internal combustion engine hydrocarbon emissions constructed in accordance with this invention is adapted for use in combination with an internal combustion engine having at least one combustion chamber, primary charge forming means for mixing air and fuel to be burned in the combustion chamber and first conduit means interconnecting the primary charge forming device with the combustion chamber. The device includes secondary charge forming means for mixing air and fuel to form a combustible mixture. The secondary charge forming means are interconnected with the combustion chamber by second conduit means. Valve means are positioned in the second conduit means and have a normally closed position and an open position permitting the passage of the air-fuel charge formed in the secondary charge forming means. Valve control means are connected to the valve means and are sensitive to the pressure present in the first conduit means. These valve control means exert a force opening the normally closed valve means whenever pressure in the first conduit means falls below a predetermined value. Pressure drops in the first conduit means thereby effectively are limited.

DESCRIPTION OF THE DRAWING The drawing is a side elevation view, partially in section, of a portion of an internal combustion engine and fuel supply system including a device for reducing internal combustion engine hydrocarbon emission that is constructed in accordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now in detail to the drawing, the numeral I0 denotes generally an internal combustion engine system including a device for the control of unburned hydrocarbon emissions. Engine 10 includes a block I2 having a plurality of combustion chambers (not shown) formed therein. Secured to block I2 is an intake manifold 14 having an internal passageway I6 fomted therethrough that communicates between the combustion chambers formed in block 12 and a carburetor 1%. This carburetor has extending therethrough an induction passageway 20 having a portion of reduced area comprising a throat 22. Fuel is directed to carburetor throat 22 in a conventional manner by suitable means (not illustrated) from the carburetor fuel bowl 24 that contains a suitable head of fuel 26. Downstream of throat 22 is a conventional carburetor throttle valve 28 pivotally mounted in the induction passage 20.

The structure described heretofore is conventional and gives rise to the problem of the engine exhausting unburned hydrocarbons during periods of engine speed deceleration from high operating speeds. During such periods, the throttle valve 28 is in the closed position illustrated, thereby effectively sealing the intake manifold passage 16 and engine block combustion chambers from the entry of ambient air. The relatively high engine speed during this period causes a severe drop in pressure (formation of vacuum) that cannot be relieved due to the closed position of the throttle valve. Fuel is being directed from the carburetor to the engine block at such times because the carburetor idle jets, not illustrated, are located downstream of the throttle valve 28.

Fuel that enters the engine combustion chambers at this time, no matter what the air-fuel mixture containing this fuel, cannot completely be combusted because of the low pressures present in the combustion chambers. It is stressed that complete combustion cannot occur at this time no matter what provisions are made in the engine charging system for maintaining a proper air-fuel mixture for combustion. It thus may be seen, that in order for complete combustion and the reduction of the emission of unburned hydrocarbons to occur, the vacuum in the combustion chambers and manifold passage I6 must be relieved. If this vacuum is relieved either by the admission of additional air or fuel into the intake manifold passage 16, the resulting air-fuel mixture that reaches the combustion chamber will be either too lean or too rich, respectively, for complete combustion, even though the combustion chamber vacuum is relieved.

This invention proposes the relief of the combustion chamber and manifold vacuum by the admission of a combustible air-fuel mixture formed in a secondary chargeforming device that includes a housing 30 defining a chamber 32. Chamber 32 is interconnected with fuel bowl 24 by means of a conduit 34). A fuel restriction orifice 36 is formed within conduit 34. The size of orifice 36 is chosen empirically to control the amount of fuel entering conduit 34. An air inlet opening 38 is formed in conduit 34 to permit the entry of air into the conduit to be mixed with fuel that passes through orifice 36. This air-fuel mixture passes through a mixture restriction opening 40 before entering chamber 32.

Chamber 32'has formed through one wall thereof an air inlet opening 42 for the admission of additionalair to further dilute the air-fuel mixture formed upstream of chamber 32. Chamber 32 is interconnected by means of an outlet passage M with a second chamber 46 that may be characterized as a valve control chamber. Chamber 46 is interconnected with manifold passage 16 by means of a conduit 48.

The passage of air-fuel mixture out of chamber 32 is controlled by a valve 50 having a valve stem 52. Although shown in the open position in the drawing, the valve 50 normally is in a closed position blocking outlet passageway 44. Valve 50 is maintained in the closed position due to the force exerted on it by a coil compression spring 54. The end of spring 54 remote from valve 50 bears upon a plate 55 that is connected to a threaded bolt 56 that extends through a threaded opening 58 in housing 30. The length of bolt 56 that extends through opening 58 may be adjusted to vary the compression of spring 54. A variance in the compression of spring 54 varies the force maintaining valve 50 in the closed position.

The end of valve stem 52 remote from valve 50 is secured to an impervious diaphragm 60 extending across chamber 46 and dividing chamber 46 into two portions. The portion of chamber 46 remote from valve stem 52 has formed in a wall thereof an opening 62 that admits atmospheric pressure into chamber 46 to act upon diaphragm 60. It thus may be appreciated that atmospheric pressure acting on diaphragm 60 is transmitted by valve stem 52 to the valve 50 and acts against the force of spring 54.

During periods of engine deceleration from high-speed operation, the extremely large drop in pressure in intake manifold 16 and the combustion cylinders of block 12 is transmitted to chamber 46 through conduit 48. The condition then exists where atmospheric pressure is present on one side of diaphragm 60 and a vacuum is present on the other side. This pressure differential results in a sufficient force being exerted by diaphragm 60 on valve 50 via valve stem 52 that the force of spring 54 is overcome and the valve is urged into the open position illustrated. With the valve open, engine vacuum is admitted to chamber 32 and conduit 34 and draws fuel through orifice 36 and air through inlet opening 38.

An air-fuel mixture thus is formed within conduit 34 and proceeds through inlet opening 40 to chamber 32 where it is further diluted by air drawn by engine vacuum through air inlet 42. The air-fuel mixture then proceeds through outlet orifice 44, chamber 46 and conduit 48 to the intake manifold conduit 16 and the engine combustion chambers.

The admission to the intake manifold and engine block of the air-fuel mixture formed in chamber 32, results in the engine vacuum being relieved. With this vacuum relieved, there is sufi'icient pressure within the engine combustion chambers so that a proper air-fuel mixture completely may be combusted. The substance relieving the vacuum, namely the air-fuel mixture formed in chamber 32, is, in itself, combustible and thus may be burned completely within the combustion chambers. With complete combustion occuring within the combustion chambers, the emission of unburned hydrocarbons through the exhaust system is minimized.

Adjustable bolt 56, that bears upon valve spring 54, allows the precise engine vacuum necessary to cause valve 50 to open to be regulated. Normally, the predetermined pressure at which valve 50 opens is a vacuum pressure slightly in excess of the pressure developed by the engine at normal idle speeds. Threaded bolt 56 may be adjusted empirically to vary the compression on spring 54 and thus the force on valve 50 until this result is achieved.

It thus may be seen that this invention provides a device for reducing internal combustion engine hydrocarbon emissions by providing for complete combustion within the engine combustion chambers by relieving the excessive engine vacuum that occurs during rapid deceleration of engine speed from high-speed operation. The device of this invention operates only when engine vacuum pressure exceeds a predetermined magnitude as measured in the engine intake manifold. At all other times, the device of this invention has no effect on engine operating conditions.

lclaim:

1. In an internal combustion engine, a device for reducing the emission of unburned hydrocarbons during periods of engine speed deceleration, said engine having a primary fucl sys em including a carburetor and an intake manifold operatively interconnecting said carburetor and at least one engine combustion chamber, said device comprising: a housing defining a chamber, first inlet means communicating with said chamber and interconnected with a source of fuel, second inlet means communicating with said chamber and allowing the entry of air into said chamber, outlet means interconnecting said chamber and said intake manifold, and pressure responsive valve means positioned in said outlet means directly responsive to pressure differentials between the atmosphere and the outlet means and being normally closed until vacuum pressure in said outlet reaches a predetermined magnitude whereupon said valve means open and allow air and fuel from said chamber to pass through said outlet means to said combustion chamber.

2. The device of claim 1, wherein the source of fuel interconnected with said first inlet means comprises a carburetor float bowl.

3. The device of claim 1, wherein said valve means comprises a valve member having a closed position blocking said outlet means and an open position, resilient means bearing on said member and exerting a force urging said member towards the closed position, and an impervious diaphragm connected to said member for movement therewith, one side of said diaphragm being exposed to atmospheric pressure and the other side of said diaphragm being exposed to the pressure in said manifold. the force of atmospheric pressure on said diaphragm acting against the force exerted by said resilient means.

4. The device of claim 3, further including adjustable means bearing on said resilient means to vary the force exerted by the latter and the predetermined pressure at which said valve member moves from the closed to the open position.

5. In combination with an internal combustion engine having at least one combustion chamber, primary charge forming means for mixing air and fuel to be burned in said combustion chamber, said primary charge-forming device being interconnected with said combustion chamber by first conduit means, secondary charge-forming means for mixing air and fuel to form a combustible mixture, said secondary charge-forming means being interconnected with said combustion chamber by second conduit means, valve means positioned in said second conduit means and having a normal closed position and an open position permitting the passage thereby of the air-fuel charge formed in the secondary chargeforming means, and valve control means connected to said valve means, said valve control means including a flexible diaphragm, one side of said diaphragm being in direct communication with the atmosphere, the other side of said atmosphere being in direct communication with the outlet means, spring means biasing said valve to a normally closed position and acting in opposition to the force exerted by the atmosphere pressure, said valve control means causing said valve to open upon the vacuum pressure within the outlet means reaching a predetermined magnitude. 

2. The device of claim 1, wherein the source of fuel interconnected with said first inlet means comprises a carburetor float bowl.
 3. The device of claim 1, wherein said valve means comprises a valve member having a closed position blocking said outlet means and an open position, resilient means bearing on said member and exerting a force urging said member towards the closed position, and an impervious diaphragm connected to said member for movement therewith, one side of said diaphragm being exposed to atmospheric pressure and the other side of said diaphragm being exposed to the pressure in said manifold, the force of atmospheric pressure on said diaphragm acting against the force exerted by said resilient means.
 4. The device of claim 3, further including adjustable means bearing on said resilient means to vary the force exerted by the latter and the predetermined pressure at which said valve member moves from the closed to the open position.
 5. In combination with an internal combustion engine having at least one combustion chamber, primary charge forming means for mixing air and fuel to be burned in said combustion chamber, said primary charge-forming device being interconnected with said combustion chamber by first conduit means, secondary charge-forming means for mixing air and fuel to form a combustible mixture, said secondary charge-forming means being interconnected with said combustion chamber by second conduit means, valve means positioned in said second conduit means and having a normal closed position and an open position permitting the passage thereby of the air-fuel charge formed in the secondary charge-forming means, and valve control means connected to said valve means, said valve control means including a flexible diaphragm, one side of said diaphragm being in direct communication with the atmosphere, the other side of said atmosphere being in direct communication with the outlet means, spring means biasing said valve to a normally closed position and acting in opposition to the force exerted by the atmosphere pressure, said valve control means causing said valve to open upon the vacuum pressure within the outlet means reaching a predetermined magnitude. 